Over the recent years, almost all pieces of work (business) have been performed making use of computers, and consequently the number of the storage devices used to retain data has increased. Moreover, it is hard to manage many storage devices, and therefore storage virtualization is done in order to mitigate the system administrator's burden, etc.
Storage virtualization is done, as schematically illustrated in FIG. 1, by connecting a plurality of storage devices and a plurality of servers through a storage virtualization apparatus cluster consisting of a plurality of storage virtualization apparatuses (not illustrated).
The storage virtualization apparatus is an apparatus capable of integrally managing all logical units of the plurality of storage devices as one virtual storage pool and extracting from the storage pool a virtual volume of arbitrary size, which is seen as one storage device by the servers.
When receiving an access request from a server to a virtual volume, the storage virtualization apparatus refers to the mapping information set in its inside, thereby specifying a storage port to which a command corresponding to the received access request is to be issued. Then, the storage virtualization apparatus issues the command to the specified storage port.